Resinous coating composition



United States Patent 3,446,784 RESINOUS COATING COMPOSITION Henry C. Kao, Dearborn, Mich., assignor, by mesne assignments, to Interchemical Corporation, New York, N.Y., a corporation of Ohio No Drawing. Filed Feb. 23, 1965, Ser. No. 434,605 Int. Cl. C08f 15/40; C08g 37/32 U.S. Cl. 26078.5 3 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a resinous coating composition, and more particularly to a coating composition comprising a vinyl interpolymer and a melamine resin which combine to result in an applied film which is particularly well adapted for outdoor applications.

It is known in the art to prepare vinyl interpolymers by polymerization of vinyl compounds with alpha, betaolefinic carboxylic acids, and to cure such resins in the presence of a melamine resin. However, there has been an unsatisfied need for such a composition having satisfactory characteristics for application to a metal substrate which is to be subjected to outdoor weathering.

For example, such compositions are desirable for painting aluminum or other metallic siding. Long strips of aluminum siding are painted at the factory and coiled into large rolls for shipment to the point of use. At the point of use, the siding is cut and formed to the requirements of the building onto which the siding is being applied. One problem which has been encountered in prior art compositions is that when the coating composition is made soft enough to have sufiicient flexibility for coiling and post-forming, it has had a degree of tackiness resulting in the layers of the roll sticking together or produces a mottling effect on the paint.

The present invention, while not restricted to use on aluminum or other metallic siding, has characteristics which make it eminently suitable for such use. It has been used in a method for applying a protective and decorative coating to siding material with subsequent coiling and post-forming and has yielded excellent results. The composition has good flexibility which permits coiling and post-forming. Its impact resistance is high, thus resisting damage due to bail or ladders being placed against the building. The composition also has good adherence to both primed and unprimed metal. The hardness is suificient for good durability, and the composition has good resistance to cracking, peeling, blistering and chipping. Additionally, the composition has excellent curing characteristics and does not require high temperatures and long periods of curing time to obtain the desired hardness and other desired properties of the applied film.

The resinous coating composition of the invention comprises from about 5 to 20% by weight of hexamethoxy- Ice methyl melamine and from about to by weight of a vinyl interpolymer. The vinyl interpolymer comprises from about 50% to 70% by weight of a monomer selected from the group consisting of ethyl acrylate, butyl acrylate and butyl methacrylate, from about 2% to 8% by weight of an acid selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid and itaconic anhydride, and from about 10% to 30% by weight of acrylonitrile. These resinous materials are dissolved in an organic solvent to which pigment and other adjuvants may be added as desired. One preferred modification of the interpolymer is the addition of a hard vinyl monomer such as methyl methacrylate, styrene or vinyl toluene. The harder monomers may be used in amounts of up to 20% by weight.

The particular melamine resin which has been chosen as a crosslinking agent for the coating composition has unexpectedly resulted in a cured film having the desired group of properties. Hexamethoxymethyl melamine is essentially monomeric. The use of a monomeric melamine resin is a departure from the standard type of melamine resin used in coating compositions, the standard type being polymeric rather than monomeric.

The preparation of hexamethoxymethyl melamine is disclosed in a publication entitled Cymel 300 issued by the American Cyanamid Company. As set forth in this publication, the structural formula is as follows:

113001120 If 1}: omoom N- /C-N\ mooHzo N omoorn The physical properties of the pure material are as The following examples are illustrative of a coating composition prepared in accordance with the present invention:

Example I.-Preparation of interpolymer A solvent mixture consisting of 60 grams of toluol, 90 grams of xylol and grams of a high solvency naphtha (B.P. 347-428 F.) were charged to a reaction vessel and heated to reflux. In a separate container, 414 grams of ethyl acrylate, 90 grams of acrylonitrile, 24 grams of glacial methacrylic acid and 72 grams of styrene were mixed with 4.8 grams of ditertiary butyl peroxide and 3.0 grams of benzoyl peroxide. The monomer peroxide mixture was slowly added at a uniform rate to the refluxing solvents in about three hours. Refiuxing was continued for two hours. 0.8 gram of di tertiary butyl peroxide in 100 grams of high solvency naphtha was added to the polymerization mass in 30 minutes. Heating at reflux was continued for another three hours and a solvent mixture containing 50 grams of high solvency naphtha and 200 grams of butyl Cellosolve acetate was added. The conversion of this polymerization reaction was 98.8 percent of theoretical. The physical constants of the resulting interpolymer were as follows:

Total nonvolatile 49.4%.

Viscosity Z3 (Gardner Bubble viscometer).

Acid number on solution 1213.

Example II.Clear baking enamel Example III.-Gloss pigmented enamel A paste consisting of 175 grams of a high grade commercial titanium dioxide, 50 grams of the interpolymer solution of Example I, 50 grams of high solvency naphtha and 25 grams of butyl Cellosolve acetate was prepared 4 substrates, such as stainless steel, copper, brass, coldrolled steel, phosphate treated steel, galvanized steel and tin plate steel, were also obtained.

This coating composition may be applied by spray application when reduced to proper spray viscosity with volatile solvents, such as ketones, esters, aromatic and semi-aromatic hydrocarbons.

Example 1V .Flat and semi-gloss enamels Enamels, varying from flat to semi-glass were produced by incorporating a colloidal silica type of inert pigment, such as Pittsburgh Plate Glass Hi-Sil 233 or Davison Chemical Syloid 162. The flattening pigment can be dispersed in the enamel composition as shown in Example III, or a separate flattening paste can be prepared by dispersing the flattening pigment in a small amount of a mixture of the interpolymer shown in Example I and the necessary solvent. This paste can then be blended with the enamel of Example III. Film properties equal to those shown in Example III were obtained when heat cured.

Pastel enamels can be prepared by tinting the white bases with colored pigment pastes. The tinting pastes are generally prepared by dispersing the colored pigments in the clear coating composition shown in Example II.

The following table of Examples V through XIV illustrates the wide scope of other interpolymers which can be cross linked with hexamethoxymethyl melamine wherein the components are recited in terms of grams:

Examples Monomers:

Acrylonitrile Acrylic Acid- V VI VII VIII IX Methaerylic Acid Itaconic Acid- Itaconic Anhydride Catalysts:

Di-t-butyl Peroxide 0. 93 0. 93

B enzoyl Peroxide t-Butyl Perbenzoate Solvents:

Tnlnene Butyl Cellosolve Acetate Methyl Isobutyl Ketone" Butanol Viscosity Z2 Z3 N.V 48.4 52.2 51.0

Xylene High Solvency Naphtha (B .1. 347 F.428 F.) 7 66. 7

High Solvency Naphtha D (B.P. 302 F.365 F.)

by dispersion in a laboratory mill to a North standard fineness of 7 /2-8. The pigment dispersion was admixed with 250 grams of the interpolymer shown in Example I, 17 grams of hexamethoxymethyl melamine, 42 grams of butyl Cellosolve acetate and 0.175 gram of silicone oil. The physical constants of the resulting enamel are:

Pigment/binder ratio 105/ 100 Total non-volatile (percent) 56.3 Interpolymer solids/hexamethoxymethyl melamine (by weight) 90/10 plication on aluminum, excellent results over other metal 7 The above interpolymers result in film properties on the same order as that of Example I when formulated into paints. Processing of these interpolymers can be carried out in a manner substantially the same as that shown in Example I.

A preferred coating composition comprises about 10% to 15% by weight of hexamethoxymethyl melamine and an interpolymer comprising from about 65% to 69% by weight of ethyl acrylate, from about 12% to 16% by weight of styrene, about 15% by weight of acrylonitrile, and about 4% by weight of methacrylic acid.

The use of acrylonitrile in the composition has been found to be very important. Enamels having an interpolymer with acrylonitrile and other enamels having a similar interpolymer without acrylonitrile have been compared. It has been found that enamel with the acrylonitrile is superior to that without. One set of test results is given in the table which follows. In conducting these tests, two enamels were prepared in the manner described previously in the examples. The interpolymers were the same excepting that one included acrylonitrile while the other did not. The enamel having an interpolymer with acrylonitrile is identified as A and the enamel having an interpolymer without acrylonitrile is identified as B:

solution from about 10% to 15% by weight of substantially monomeric hexamethoxymethyl melamine, from Adhesion Adhesion Pencil Enamel Reverse Over Impact Flexibility Over Bend Hardness Acetone Metal Substrata No. Baking Schedule Impact Bump (0.1. Bend) Edge (Passes) Resistance Stainless Steel J60 seconds at 525 F 32 91/62 gf A 60 seconds at 525 F 8 (135) 8 8 8 F Fair-Good. No. 1000 Bonderite Steel us B 60 seconds at 525 F 5 (135) 3 0 F Fair. Tin Dipped Steel fig: ":}60 seconds at 525 F...- g g g Galvanized Steel do g g g a b A 60 seconds at 525 F"-.. 8% (135) 8% 9% 9% F Fair-Good. Cold Rolled Steel p s 12 60 seconds at 525 F.-. g g 8; g Geog. g 9 2 2 0. Copper }60 seconds at 525 F 5 3 7 5 g E D0.

. A 10- -5 10 9 1 xcellent. Tm Plate Steel 9% 9 3 o F Do.

Figures in parenthesis are pound-inch impact values.

As can be seen from the table, cured films of enamels about 85% to 90% by weight of an interpolymer consist- A and B showed about equal hardness and acetone resistance. The other film properties, however, namely, impact resistance, flexibility and adhesion were superior in enamel A, wherein the interpolymer contained acrylonitrile, as compared to enamel B, wherein the interpolymer did not contain acrylonitrile.

Having thus described my invention, I claim:

1. A resinous coating composition consisting essentially ing essentially of (a) from about 65% to 69% by weight of ethyl acrylate, (b) from about 12% to 16% by weight of styrene, (0) about 4% by weight of methacrylic acid, and ((1) about 15% by weight of acrylonitrile.

3. A metal sheet having a cured coating on at least one face surface thereof, said coating produced from said resinous coating composition as defined in claim 1.

of a volatile organic solvent containing in solution from f r n s Cited about 5% to 20% by weight of substantially monomeric U T D S ATES PATENTS hexamethoxymethyl melamine, from about 80% to 95% by weight of an interpolymer consisting essentially of izli 5 6 (a) from about to by weight of a monomer i a selected from the group consisting of ethyl acrylate, butyl 35 32 Tlscfibem 117 16i acrylate and butyl methacrylate, (b) from about 0% to 3 1 5 Sm) e 260*? 20% by weight of a monomer selected from the group 6 0 196 Petropoulos et 260 853 consisting of methyl methacrylate, styrene and vinyl 3215678 11/1965 Apelman 260 '8 toluene, (c) from about 2% to 8% by weight of an acid selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid and itaconic anhydride, and (d) from about 10% to 30% by Weight of aorylonitrile.

2. A liquid resinous coating composition consisting essentially of a volatile organic solvent containing in 

